Walter Thurmond III knows a winner when he sees one, and he loves what he sees in the Giants.

After four seasons in Seattle helping the Seahawks build toward last year’s Super Bowl title as the nickel cornerback in their celebrated “Legion of Boom’’ secondary, Thurmond signed a one-year, $3.5 million deal with the Giants in March, adding an immediate dose of swagger to their defense.

Thurmond is a confident player with a colorful personality (see the shiny gold lamé dress-suit-with-shorts outfit he wore to the ESPY Awards in Los Angeles last month) who is also very observant of his surroundings.

Drafted in Pete Carroll’s first year with the Seahawks (2010), Thurmond watched the former Jets coach methodically build a winner in Seattle, where winning was scarce for most of the franchise’s existence.

When he became a free agent seeking a new opportunity for more money than he could make staying in Seattle, the Giants were the team Thurmond targeted because of the franchise’s winning tradition. He felt he did not need to help build it as much as fit into it.

“This is one of the reasons why I came over there — to win a championship,’’ Thurmond told The Post on Tuesday. “I most definitely know what it takes to win that championship. When I was in Seattle, I was helping to build that program up. Now, I’m coming into a situation where there is a tradition of winning. That’s what you live for. Once you get one championship, you want to keep winning. Now that I’ve broken the seal, that’s all I want.’’

Thurmond and the Seahawks “broke the seal’’ at MetLife Stadium, which stands about a half-dozen Eli Manning heaves from the Giants training facility from where he spoke Tuesday.

Thurmond said he was attracted to the Giants because he wanted to help them “get back to that championship-caliber mindset that they’re used to having around here.’’

He also was drawn to coach Tom Coughlin, who is as close to the complete opposite of Carroll as you can be.

“They’re both championship coaches,’’ Thurmond said. “It’s crazy, because Coughlin is the oldest head coach in the league (67) and Pete is the second-oldest head coach (62), so you would naturally think that Pete would be leaning toward the same sort of mindset that Coach Coughlin has, but it’s completely different — day and night as far as their personalities.

“Pete is a kid at heart. Coach Coughlin knows how to win. They had a down year last year, but I know he really wants to get back to that championship caliber of 2007 and 2011 and we have the talent to be able to do it.’’

Thurmond burns to be a part of helping bring the Giants to a third Super Bowl in eight years, and he’s not afraid to say so.

He was not a Giant for more than what seemed like 10 minutes before Thurmond, perhaps thinking he had signed with Rex Ryan’s Jets instead of Coughlin’s Giants, was brashly telling reporters this during the offseason workout period in April: “I’m the best slot corner in the league.”

That sparked a Twitter tête-à-tête between Thurmond and Eagles nickel back Brandon Boykin, who had six picks in 2013 compared to Thurmond’s one.

Hours after Thurmond made his bold proclamation, Boykin tweeted: “But who is Walter Thurmond??’’

Thurmond responded: “I think its funny that boykins is upset about the best nickel comment when he starts on the outside! Shouldn’t he have higher aspirations’’

To which Boykin responded: “”I don’t start on the outside.. My stats are probably what confused u though. I understand.”

On Tuesday, Thurmond did not back away from his April claim, but he insisted it did not come from being blindly cocky.

“One of the reasons I said I was the best was because I didn’t give up a touchdown last year; I have a confidence about myself that I’m the best out there,’’ he said.

Thurmond’s teammates have quickly taken to him. In fact, after a Jayron Hosley interception in a 7-on-7 drill Tuesday, Thurmond, who wasn’t even in on the play, playfully escorted Hosley into the end zone for the pick-6.